1. Field
The present invention relates to an apparatus for inserting catheters or endoscopic devices into a body cavity, the apparatus having a valve, which is provided with a housing with a cup-shaped recess bounded by a base, wherein a first channel section is provided in the base of the recess, with a plunger with an end face, wherein the plunger can at least in part be inserted into the cup-shaped recess and wherein a second channel section is provided in the plunger, and with an elastic seal arranged within the cup-shaped recess, wherein a third channel section is provided in the seal, wherein said third channel forms together with the first channel section in the base of the recess of the housing and the second channel section in the plunger a central channel, which central channel is continuous along a longitudinal axis.
2. Related Prior Art
Such introduction shuttle systems or trocars, which, for example, are used for vascular accesses or in endoscopic operations, are well-known from the prior art.
By way of example, U.S. Pat. No. 5,300,035 describes a trocar of the type mentioned at the outset, in which a proximal sealing mechanism is provided. This sealing mechanism is formed by a Tuohy-Borst valve.
The valve consists of a cup-shaped housing with a cup base and a screw top, which closes off the housing at the cup opening facing away from the cup base. In the direction of the cup base, the screw top has a plunger, which butts against an elastic seal accommodated in the housing. Here, the elastic seal is clamped between the cup base and the end face of the plunger. A central channel, formed by a plurality of channel sections, is routed through the cup base, the elastic seal and the plunger.
If the screw top is screwed into the housing, as a result of which the plunger is moved in the direction of the cup base, the seal situated between cup base and plunger is deformed such that the central channel is narrowed such that the inner diameter thereof is reduced.
Thus, such a sealing mechanism allows the formation of openings with variable diameters, which can then tightly seal an endoscopic instrument or a catheter routed through the central channel in relation to the environment or in relation to an internal liquid pressure or gas pressure. A disadvantage of the known introduction sheath is that leaks may occur as a result of the described embodiment of the valve.
This is because the constriction of the channel running through the seal, which constriction is required for the sealing effect, is based solely on the elastic deformation of the seal.
If the seal is compressed along its longitudinal axis, it is deformed such that there is a thickening in the wall. Since the walls of the cup-shaped recess restrict a radial expansion of the seal towards the outside, the thickening of the wall acts in the direction of the inner diameter of the seal, as a result of which the third channel section, running in the interior of the seal, narrows.
The seal material can thus in an interlocking fashion butt against a device, for example a catheter, situated in the interior of the channel, as a result of which the third channel section is sealed in relation to the inserted device.
In the process, a disadvantage of the known and other apparatuses with conventional Tuohy-Borst valves is that this only allows a relatively small constriction of the third channel section.
This emerges from the fact that the conventional seals, arranged in a Tuohy-Borst valve, are relatively stiff in the longitudinal direction, and so a high deformation resistance has to be overcome during the compression along the longitudinal axis; moreover, this resistance increases as the third channel section becomes ever narrower.
Thus, much force needs to be exerted for the compression in the known apparatuses in order to bring about an appreciable constriction of the channel.
A further disadvantage here is that only part of the force exerted to twist the screw top in relation to the cup-shaped housing acts in the longitudinal direction on the seal. As a result of the deformation resistance of the seal, there is gradually increasing friction between seal and screw top with increasing degree of constriction. In order to continue closing the valve, this friction must be overcome in addition to the increasing deformation resistance of the seal.
After a certain degree of constriction, the forces to be overcome become so large that a secure seal can no longer be ensured.
The above-described effect becomes even more pronounced if an asymmetric device, or an asymmetrically deformable device, for example a catheter with an off-centred guide wire, is routed through a conventional apparatus with a Tuohy-Borst valve.
This is because the seal contacts the regions of the device first that have the greatest extent perpendicular to the longitudinal axis. In the process, forces build up between the device and the seal that counter further closing of the seal. Thus, there is no sealing abutment between seal and catheter at those points on the catheter that have a smaller extent perpendicularly to the longitudinal axis.
However, leaks should be avoided for functional and medical considerations. On the one hand, bodily fluids, such as blood, can leak out through such leaks and thus adversely affect the handling or functionality of the introduction sheath and can also result in unnecessary additional contamination of the surgical surroundings, including an increased risk of infection for the operator. On the other hand, contaminants can also penetrate into the interior of the sheath shell through such leaks and may, for example, cause septic complications.
In the case of trocars, such leaks can result in a gas leak, particularly in the case of ventilating the abdominal cavity, and so the success of endoscopic operations on the internal organs is jeopardized or the complication rate is increased.
As a consequence of this, either the operator must select a very narrow valve at the very beginning, as a result of which the selection of catheters or endoscopic devices to be used is severely limited, or a valve with a larger inner diameter is selected, which may then, in certain circumstances, not be able to ensure a complete seal.
A further disadvantage of the known apparatuses lies in the difficult handling thereof.
While the operator must, on the one hand, as far as possible keep the position of the apparatus constant, a two-handed operation of the screw valve is required at the same time, for example when a catheter or an endoscopic device is inserted. Thus, depending on the situation, two people are required in order to be able to operate the conventional apparatuses safely.